Rubbery polymers with improved color stability

ABSTRACT

There is a need for polymers which are utilized in automotive interiors which offer good color stability as well as a high level of heat and ultraviolet light resistance. It is particularly critical for polymers which are utilized in making skin compounds for automotive instrument and door panels to have excellent color stability as well as excellent heat and ultraviolet light resistance. This invention discloses a rubbery polymer which can be blended with polyvinyl chloride to make leathery compositions having good color stability, heat resistance and ultraviolet light resistance, said rubbery polymer being comprised of repeat units which are derived from (a) butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e) a conjugated diene monomer and (f) a crosslinking agent; wherein the repeat units which are derived from the conjugated diene monomer are epoxidized. Such leathery compositions offer an excellent combination of properties for utilization in making skin compounds for panels used in automotive applications.

This is a Divisional of application Ser. No. 08/895,652, filed on Jul.17, 1997, now U.S. Pat. No. 5,753,772.

BACKGROUND OF THE INVENTION

Automotive instrument panels and door panels are typically compositeswhich are made of a rigid backing which supports a semi-rigid urethanefoam with the semi-rigid urethane foam being covered with a skincompound. Such skin compounds are typically blends of polyvinyl chloride(PVC) with a nitrile rubber (NBR). The nitrile rubber is included insuch blends as a permanent modifier for the PVC which provides it with ahigher degree of flexibility.

The automotive industry is currently moving toward more aerodynamic bodydesigns. These new aerodynamic designs typically include larger glasssurface areas. Such design changes have significantly increased the heatand ultraviolet light aging requirements of automotive interiors. Thishas, in turn, significantly increased the demands put upon polymersutilized as skins in automotive interior panels.

Heat and light stabilizers can be employed to improve the heat andultraviolet light aging characteristics of conventional PVC/NBR blendswhich are utilized as skins for automotive interior panels. However, thedegree to which the aging characteristics of such blends can be improvedby the addition of additives is limited. In fact, there is a demand forperformance characteristics in such applications which cannot berealized by the utilization of heat and light stabilizers alone. Forinstance, it would be highly desirable for the skins used in automotivepanels to resist discoloration and cracking under conditions of highheat and intense ultraviolet light throughout the life of the vehicle.

NBR/PVC blends offer an array of physical properties making them usefulas a skin composition for automotive panels. The NBR acts as a permanentflexibilizing monomer for the PVC. It also acts as a shrinkage controlagent, and embossing aid, and improves grain retention. The NBR in suchblends further provides vacuum-forming gauge control and exhibits lowfog characteristics. NBR is highly compatible with PVC and has thecapability of being recycled. It is essential for any polymer that issubstituted for NBR to display these essential characteristics.

U.S. Pat. No. 5,380,785 discloses rubbery polymer which can be blendedwith polyvinyl chloride to make leathery compositions having good heatand ultraviolet light resistance, said rubbery polymer being comprisedof repeat units which are derived from (a) butyl acrylate, or optionallya mixture of butyl acrylate and 2-ethylhexyl acrylate containing up toabout 40 percent 2-ethylhexyl acrylate, (b) at least one member selectedfrom the group consisting of methyl methacrylate, ethyl methacrylate,methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e)a half ester maleate soap and (f) a crosslinking agent. However, itwould be highly desirable to increase the color stability of suchrubbery polymers.

SUMMARY OF THE INVENTION

The present invention relates to a rubbery polymer that can be blendedwith PVC to make leathery compositions. These compositions areparticularly useful in manufacturing skins for automotive interiorpanels. Skin compositions that are made utilizing this rubbery polymerprovide a higher level of resistance to heat and ultraviolet light thanthose made utilizing conventional NBR/PVC blends. They also offergreatly improved color stability. The rubbery polymers of this inventionalso offer low fog characteristics, low odor, shrinkage control andgrain retention. They also act as an embossing aid and as a permanentflexibilizing modifier. The rubbery polymers of this invention also havecharacteristics that make them useful in building gasket applications.

This invention more specifically discloses a rubbery polymer which canbe blended with polyvinyl chloride to make leathery compositions havinggood color stability, heat resistance and ultraviolet light resistance,said rubbery polymer being comprised of repeat units which are derivedfrom (a) butyl acrylate, or optionally a mixture of butyl acrylate and2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexylacrylate, (b) at least one member selected from the group consisting ofmethyl methacrylate, ethyl methacrylate, methyl acrylate and ethylacrylate, (c) acrylonitrile, (d) styrene, (e) a conjugated diene monomerand (f) a crosslinking agent; wherein the repeat units which are derivedfrom the conjugated diene monomer are epoxidized.

The subject invention further reveals a process for preparing a rubberypolymer which can be blended with polyvinyl chloride to make leatherycompositions having improved color stability as well as good heat andultraviolet light resistance, said process comprising the steps of (1)polymerizing (a) butyl acrylate, or optionally a mixture of butylacrylate and 2-ethylhexyl acrylate containing up to about 40 percent2-ethylhexyl acrylate, (b) at least one member selected from the groupconsisting of methyl methacrylate, ethyl methacrylate, methyl acrylateand ethyl acrylate, (c) acrylonitrile, (d) a conjugated diolefin monomerand (e) a crosslinking agent under emulsion polymerization conditions toproduce a seed polymer containing latex; (2) adding (a) styrene, (b)additional acrylonitrile, (c) additional conjugated diolefin monomer and(d) additional crosslinking agent to the seed polymer containing latexunder emulsion polymerization conditions which result in the formationof an emulsion containing the rubbery polymer; (3) epoxidizing therubbery polymer; and (4) recovering the rubbery polymer from theemulsion containing the rubbery polymer.

The subject invention further reveals a process for preparing a rubberypolymer which can be blended with polyvinyl chloride to make leatherycompositions having improved tensile properties as well as good heat andultraviolet light resistance, said process comprising the steps of (1)polymerizing (a) butyl acrylate, or optionally a mixture of butylacrylate and 2-ethylhexyl acrylate containing up to about 40 percent2-ethylhexyl acrylate, (b) at least one member selected from the groupconsisting of methyl methacrylate, ethyl methacrylate, methyl acrylateand ethyl acrylate, (c) acrylonitrile, (d) a conjugated diolefin monomerand (e) a crosslinking agent under emulsion polymerization conditions toproduce a seed polymer containing latex; (2) adding (a) styrene, (b)additional acrylonitrile, (c) additional conjugated diolefin monomer and(d) additional crosslinking agent to the seed polymer containing latexunder emulsion polymerization conditions which result in the formationof an emulsion containing the rubbery polymer; (3) ozonating the rubberypolymer; and (4) recovering the rubbery polymer from the emulsioncontaining the rubbery polymer.

The present invention also discloses a leathery composition which isuseful in automotive applications which is comprised of (1) polyvinylchloride, (2) a plasticizer and (3) a rubbery polymer which is comprisedof repeat units which are comprised of (a) butyl acrylate, or optionallya mixture of butyl acrylate and 2-ethylhexyl acrylate containing up toabout 40 percent 2-ethylhexyl acrylate, (b) at least one member selectedfrom the group consisting of methyl methacrylate, ethyl methacrylate,methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e)a conjugated diolefin monomer and (f) a crosslinking agent, wherein therubbery polymer is epoxidized.

The subject invention further reveals a panel for automotiveapplications which is comprised of a semirigid urethane foam which issupported by a rigid backing, wherein said semirigid urethane foam iscovered with a leathery skin which is comprised of (1) polyvinylchloride, (2) a plasticizer and (3) a rubbery polymer which is comprisedof repeat units which are comprised of (a) butyl acrylate, or optionallya mixture of butyl acrylate and 2-ethylhexyl acrylate containing up toabout 40 percent 2-ethylhexyl acrylate, (b) at least one member selectedfrom the group consisting of methyl methacrylate, ethyl methacrylate,methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e)a conjugated diolefin monomer and (f) a crosslinking agent, wherein saidrubbery polymer is epoxidized.

The present invention also discloses a leathery composition which isuseful in automotive applications which is comprised of (1) polyvinylchloride, (2) a plasticizer and (3) a rubbery polymer which is comprisedof repeat units which are comprised of (a) butyl acrylate, or optionallya mixture of butyl acrylate and 2-ethylhexyl acrylate containing up toabout 40 percent 2-ethylhexyl acrylate, (b) at least one member selectedfrom the group consisting of methyl methacrylate, ethyl methacrylate,methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e)a conjugated diolefin monomer and (f) a crosslinking agent, wherein therubbery polymer is ozonated.

The subject invention further reveals a panel for automotiveapplications which is comprised of a semirigid urethane foam which issupported by a rigid backing, wherein said semirigid urethane foam iscovered with a leathery skin which is comprised of (1) polyvinylchloride, (2) a plasticizer and (3) a rubbery polymer which is comprisedof repeat units which are comprised of (a) butyl acrylate, or optionallya mixture of butyl acrylate and 2-ethylhexyl acrylate containing up toabout 40 percent 2-ethylhexyl acrylate, (b) at least one member selectedfrom the group consisting of methyl methacrylate, ethyl methacrylate,methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e)a conjugated diolefin monomer and (f) a crosslinking agent, wherein saidrubbery polymer is ozonated.

DETAILED DESCRIPTION OF THE INVENTION

The rubbery polymers of this invention are synthesized utilizing a freeradical emulsion polymerization technique. These rubbery polymers arecomprised of repeat units which are derived from (a) butyl acrylate, oroptionally a mixture of butyl acrylate and 2-ethylhexyl acrylatecontaining up to about 40 percent 2-ethylhexyl acrylate, (b) methylmethacrylate, ethyl methacrylate, methyl acrylate or ethyl acrylate, (c)acrylonitrile, (d) styrene, (e) a conjugated diolefin monomer and (f) acrosslinking agent. The crosslinking agent is typically amulti-functional acrylate, a multi-functional methacrylate ordivinylbenzene. Some specific examples of crosslinking agents which canbe used include ethylene glycol methacrylate, divinylbenzene and1,4-butanediol dimethacrylate.

Technically, the rubbery polymers of this invention contain repeat units(chain linkages) which are derived from (a) butyl acrylate, oroptionally a mixture of butyl acrylate and 2-ethylhexyl acrylatecontaining up to about 40 percent 2-ethylhexyl acrylate, (b) methylmethacrylate, ethyl methacrylate, methyl acrylate or ethyl acrylate, (c)acrylonitrile, (d) styrene, (e) a conjugated diolefin monomer and (f) acrosslinking agent. These repeat units differ from the monomers thatthey were derived from in that they contain one less carbon--carbondouble bond than is present in the respective monomer. In other words, acarbon-to-carbon double bond is consumed during the polymerization ofthe monomer into a repeat unit in the rubbery polymer. Thus, in sayingthat the rubbery polymer contains various monomers, in actuality meansthat it contains repeat units that are derived from those monomers.

The rubbery polymers of this invention will normally contain (a) fromabout 40 weight percent to about 80 weight percent butyl acrylate, oroptionally a mixture of butyl acrylate and 2-ethylhexyl acrylatecontaining up to 40 weight percent 2-ethylhexyl acrylate, (b) from about3 weight percent to about 35 weight percent methyl methacrylate, ethylmethacrylate, methyl acrylate or ethyl acrylate, (c) from about 4 weightpercent to about 30 weight percent acrylonitrile, (d) from about 3weight percent to about 25 weight percent styrene, (e) from about 4weight percent to about 20 weight percent of a conjugated diolefinmonomer and (f) from about 0.25 weight percent to about 8 weight percentof a crosslinking agent.

Such rubbery polymers will preferably contain (a) from about 50 weightpercent to about 77 weight percent butyl acrylate, or optionally amixture of butyl acrylate and 2-ethylhexyl acrylate containing up toabout 40 percent 2-ethylhexyl acrylate, (b) from about 5 weight percentto about 25 weight percent of at least one member selected from thegroup consisting of methyl methacrylate, ethyl methacrylate, methylacrylate and ethyl acrylate, (c) from about 5 weight percent to about 30weight percent acrylonitrile, (d) from about 5 weight percent to about18 weight percent styrene, (e) from about 6 weight percent to about 16weight percent of a conjugated diolefin monomer and (f) from about 0.5weight percent to about 4 weight percent of a crosslinking agent.

The rubbery polymers of this invention will more preferably be comprisedof repeat units which are derived from (a) about 55 weight percent toabout 75 weight percent butyl acrylate, or optionally a mixture of butylacrylate and 2-ethylhexyl acrylate containing up to about 40 percent2-ethylhexyl acrylate, (b) about 5 weight percent to about 20 weightpercent of at least one member selected from the group consisting ofmethyl methacrylate, ethyl methacrylate, methyl acrylate and ethylacrylate, (c) about 6 weight percent to about 20 weight percentacrylonitrile, (d) about 6 weight percent to about 14 weight percentstyrene, (e) about 7 weight percent to about 14 weight percent of aconjugated diolefin monomer and (f) about 1 weight percent to about 3weight percent of a crosslinking agent. The percentages reported in thisparagraph are based upon the total weight of the rubbery polymer.

The rubbery polymers of the present invention are synthesized in anaqueous reaction mixture by utilizing a free radical polymerizationtechnique. The reaction mixture utilized in this polymerizationtechnique is comprised of water, the appropriate monomers, a suitablefree radical initiator, a crosslinking agent and a soap. It is oftenpreferred to utilize a metal salt of an alkyl sulfonate or a metal saltof an alkyl sulfate as the soap. The reaction mixture utilized in thispolymerization technique will normally contain from about 10 weightpercent to about 80 weight percent monomers, based upon the total weightof the reaction mixture. The reaction mixture will preferably containfrom about 20 weight percent to about 70 weight percent monomers andwill more preferably contain from about 40 weight percent to about 50weight percent monomers.

The reaction mixtures utilized in carrying out such polymerizations willtypically contain from about 0.005 phm (parts per hundred parts ofmonomer by weight) to about 1 phm of at least one member selected fromthe group consisting of metal salts of alkyl sulfates and metal salts ofalkyl sulfonates. It is generally preferred for the reaction mixture tocontain from about 0.008 phm to about 0.5 phm of the metal salt of thealkyl sulfonate or the metal salt of the alkyl sulfate. It is normallymore preferred for the reaction mixture to contain from about 0.05 phmto about 0.3 phm of the metal salt of the alkyl sulfonate or the metalsalt of the alkyl sulfate.

The free radical polymerization technique utilized in this synthesis isnormally initiated by including a free radical initiator in the reactionmixture. Virtually, any type of compound capable of generating freeradicals can be utilized as the free radical initiator. The free radicalgenerator is normally employed at a concentration within the range ofabout 0.01 phm to about 1 phm. The free radical initiators which arecommonly used include the various peroxygen compounds such as potassiumpersulfate, ammonium persulfate, benzoyl peroxide, hydrogen peroxide,di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide,decanoyl peroxide, lauryl peroxide, cumene hydroperoxide, p-menthanehydroperoxide, t-butyl hydroperoxide, acetyl peroxide, methyl ethylketone peroxide, succinic acid peroxide, dicetyl peroxydicarbonate,t-butyl peroxyacetate, t-butyl peroxymaleic acid, t-butylperoxybenzoate, acetyl cyclohexyl sulfonyl peroxide, and the like; thevarious azo compounds such as 2-t-butylazo-2-cyanopropane, dimethylazodiisobutyrate, azodiisobutylronitrile,2-t-butylazo-1-cyanocyclohexane, 1-t-amylazo-1-cyanocyclohexane, and thelike, the various alkyl perketals, such as 2,2-bis-(t-butyl-peroxy)butane, and the like. Water-soluble peroxygen-free radical initiatorsare especially useful in such aqueous polymerizations.

The emulsion polymerizations of this invention are typically carried outat the temperature which is within the range of about 10° C. to about95° C. At temperatures above about 88° C., alkyl acrylate monomers (suchas butyl acrylate) have a tendency to boil. Thus, a pressurized jacketwould be required for heating such alkyl acrylate monomers totemperatures in excess of about 80° C. Thus, in most cases, thepolymerization temperature utilized will vary between about 20° C. andabout 80° C. On the other hand, at polymerization temperatures of lessthan about 55° C., a redox initiator system is required to insuresatisfactory polymerization rates.

The sulfonate surfactants that are useful in this invention arecommercially available from a wide variety of sources. For instance, DuPont sells sodium alkylarylsulfonate under the tradename Alkanol™,Browning Chemical Corporation sells sodium dodecylbenzene sulfonatesunder the tradename Ufaryl™ Dl-85 and Ruetgers-Nease Chemical Companysells sodium cumene sulfonate under the tradename Naxonate Hydrotrope™.Some representative examples of sulfonate surfactants which can be usedinclude sodium toluene-xylene sulfonate, sodium toluene sulfonate,sodium cumene sulfonates, sodium decyldiphenylether sulfonate, sodiumdodecylbenzenesulfonate, sodium dodecyldiphenylether sulfonate, sodium1-octane sulfonate, sodium tetradecane sulfonate, sodium pentadecanesulfonate, sodium heptadecane sulfonate and potassium toluene sulfonate.

Metal salts of alkylbenzene sulfonates are a highly preferred class ofsulfonate surfactant. The metal will generally be sodium or potassiumwith sodium being preferred. Sodium salts of alkylbenzene sulfonateshave the structural formula: ##STR1## wherein R represents an alkylgroup containing from 1 to about 20 carbon atoms. It is preferred forthe alkyl group to contain from about 8 to about 14 carbon atoms.

The polymerization is carried out as a two-step batch process. In thefirst step, a seed polymer containing latex is synthesized. This is doneby polymerizing (a) butyl acrylate, or optionally a mixture of butylacrylate and 2-ethylhexyl acrylate containing up to about 40 percent2-ethylhexyl acrylate, (b) at least one member selected from the groupconsisting of methyl methacrylate, ethyl methacrylate, methyl acrylateand ethyl acrylate, (c) acrylonitrile, (d) a conjugated diolefin monomerand (d) a crosslinking agent.

The seed polymer containing latex is typically prepared by thepolymerization of a monomer mixture which contains about 40 to about 90weight percent butyl acrylate, or optionally a mixture of butyl acrylateand 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexylacrylate, from about 1 to about 35 weight percent methyl methacrylate,ethyl methacrylate, methyl acrylate or ethyl acrylate, from about 2 toabout 30 weight percent acrylonitrile, from about 2 to about 30 weightpercent of a conjugated diolefin monomer and from about 0.25 weightpercent to 6 weight percent of the crosslinking agent. It is typicallypreferred for the monomeric component utilized in the first step toinclude about 50 weight percent to about 85 weight percent butylacrylate or optionally a mixture of butyl acrylate and 2-ethylhexylacrylate containing up to about 40 percent 2-ethylhexyl acrylate, fromabout 2 weight percent to about 20 weight percent ethyl acrylate, ethylmethacrylate, methyl acrylate or methyl methacrylate, from about 4weight percent to about 28 weight percent acrylonitrile, from about 4weight percent to about 25 weight percent of a conjugated diolefinmonomer and from about 0.25 weight percent to about 4 weight percent ofthe crosslinking agent. It is generally more preferred for the monomercharge composition used in synthesizing the seed polymer latex tocontain from about 60 weight percent to about 80 weight percent butylacrylate, or optionally a mixture of butyl acrylate and 2-ethylhexylacrylate containing up to about 40 percent 2-ethylhexyl acrylate, fromabout 3 weight percent to about 20 weight percent methyl methacrylate,ethyl methacrylate, methyl acrylate or ethyl acrylate, from about 5weight percent to about 20 weight percent acrylonitrile, from about 6weight percent to about 20 weight percent of a conjugated diolefinmonomer and from about 0.25 weight percent to about 2 weight percentcrosslinking agent.

After the seed polymer latex has been prepared, styrene monomer,additional acrylonitrile monomer, additional conjugated diolefin monomerand additional crosslinking agent is added to the seed polymercontaining latex. As a general rule, from about 5 parts by weight toabout 80 parts by weight of styrene, from about 5 part by weight toabout 50 parts by weight of additional acrylonitrile, from about 2 partsby weight to about 40 parts by weight of additional conjugated diolefinmonomer and from about 0.25 to 15 parts by weight of the crosslinkingagent will be added. In this second stage of the polymerization, it ispreferred to add from about 20 parts by weight to about 75 parts byweight of styrene, from about 15 parts by weight to about 40 parts byweight of acrylonitrile, from about 4 parts by weight to about 30 partsby weight of conjugated diolefin monomer and from about 1 part by weightto 10 part by weight of the crosslinking agent. It is typically morepreferred for from about 50 parts by weight to about 70 parts by weightof styrene, from about 20 parts by weight to about 35 parts by weight ofacrylonitrile, from about 5 parts by weight to about 20 parts by weightof conjugated diolefin monomer and from about 3 parts by weight to about7 parts by weight of the crosslinking agent to be added to the seedpolymer latex to initiate the second phase of the polymerization.

A wide variety of crosslinking agents can be utilized in carrying outthe polymerizations of this invention. Some representative examples ofcrosslinking agents that can be utilized include difunctional acrylates,difunctional methacrylates, trifunctional acrylates, trifunctionalmethacrylates and divinylbenzene. The crosslinking agent proven to beparticularly useful is 1,4-butanediol dimethacrylate. The conjugateddiolefin monomers that can be employed will typically contain from 4 toabout 8 carbon atoms. Isoprene and 1,3-butadiene are preferredconjugated diolefin monomers with 1,3-butadiene being the mostpreferred.

In most cases, the polymerization will be continued until a high monomerconversion has been attained. After the polymerization has beencompleted, the rubbery polymer will be epoxidized to improve colorstability or ozonated to improve tensile properties. The rubbery polymercan, of course, be both epoxidized and ozonated to improve both of thesecharacteristics. In any case, the rubbery polymer is epoxidized and/orozonated while it is still in the emulsion.

The rubbery polymer can be epoxidized by simply adding a peracid, suchas perbenzoic acid or performic acid, to the latex containing therubbery polymer. To insure that all of the double bonds in the rubberypolymer undergo epoxidation, an excess of the peracid will normally beadded. It should be noted that one mole of double bonds will be presentin the rubbery polymer for every mole of conjugated diolefin monomeremployed in its synthesis.

It is normally convenient to form the peracid in situ in the latex ofthe rubbery polymer. For instance, performic acid (methaneperoxoic acid)can be generated in situ in the latex by reacting formic acid withhydrogen peroxide. This reaction will typically be conducted in thepresence of acetic acid which acts as a catalyst. Thus, the epoxidationcan conveniently be done by adding formic acid, hydrogen peroxide andacetic acid to the latex of the rubbery polymer. The epoxidation of therubbery polymer will typically be carried out at a temperature which iswithin the range of about 70° F. (21° C.) to about 140° F. (60° C.) Itis normally preferred for the epoxidation to conducted at a temperaturewhich is within the range of about 90° F. (32° C.) to about 130° F. (54°C.) with it being most preferred for the epoxidation to be conducted ata temperature which is within the range of about 110° F. (43° C.) toabout 120° F. (49° C.).

The rubbery polymer can be ozonated by simply mixing ozone into thelatex of the rubbery polymer for a period of time which is sufficient toattain the desired results. This can be accomplished by bubbling ozonethrough the latex. It can also be done by rapidly agitating the latexunder an ozone containing atmosphere. It may be desirable for the ozonecontaining atmosphere to be under pressure. Other techniques for mixingozone throughout the latex being treated can also be employed inpracticing the present invention.

The temperature at which this treatment procedure is carried out is notcritical. In fact, virtually any temperature between the freezing pointof the latex and its boiling point can be utilized. However, forpractical reasons, the latex will normally be treated with ozone at atemperature which is within the range of about 0° C. to about 60° C. Atemperature within the range of about 15° C. to about 30° C. will mostpreferably be employed. Higher temperatures can result in reducedsolubility of the ozone in the latex even though faster reaction ratesmay be attained. The ozone treatment will be carried out for a timewhich is sufficient to ozonate a sufficient number of double bonds inthe polymer to attain the tensile properties which are desired. Thetreatment time employed will typically be within the range of about 15minutes to about 6 hours. The period of time utilized in treating thelatex with ozone will more typically be within the range of about 30minutes to about 2 hours.

The reaction through which ozone cleaves the double bonds in the rubberypolymer can be depicted as follows: ##STR2## In the absence of zinc,hydrogen peroxide is formed which may degrade the carbonyl productsformed by oxidation. In such a scenario, the hydrogen peroxide reactswith the aldehydes produced by ozonylsis and converts them to carboxylicacids. A more detailed description of ozonolysis is provided by J March,Advanced Organic Chemistry: Reactions, Mechanisms and Structure; pages871-874 (McGraw-Hill Book Company, 1968) and by R T Morrison and R NBoyd, Organic Chemistry; Third Edition; pages 218-219 (Allyn and Bacon,Inc., 1973).

If the ozonylsis is carried out in the absence of zinc, carboxyl groupswill typically be formed. As the amount of carboxyl groups on thepolymer increases, the pH of the emulsion decreases. The extent to whichdouble bonds in the polymer have been cleaved can accordingly bemonitored by monitoring the pH of the emulsion.

After the epoxidation and/or ozonylsis step has been completed, it isnormally desirable to add an aminoalcohol to the emulsion to deodorizethe latex. The aminoalcohol will generally be of the structural formulaHO--A--NH₂ wherein A represents an alkylene group which contains from 2to about 20 carbon atoms. It is normally preferred for the aminoalcoholto contain from 2 to about 10 carbon atoms with amino alcohols whichcontain from 2 to about 5 carbon atoms being most preferred.Ethanolamine (HO--CH₂ --CH₂ --NH₂) which is also known as 2-aminoethanoland 2-hydroxyethylamine is a representative example of a highlypreferred aminoalcohol. Some additional examples of preferredaminoalcohols include 3-aminopropanol, 4-aminobutanol,2-amino-2-methyl-1-propanol, 2-amino-2-ethyl-1,3- propanediol,N-methyl-2,2-iminoethanol and 5-aminopentanol.

This deodorizing step will be carried out under conditions which allowfor the aminoalcohol to react with residual n-butylacrylate andacrylonitrile which is present in the emulsion. This reaction willproceed over a broad temperature range and the deodorizing step can beconducted at any temperature which is within the range of about 5° C.and about 95° C. However, for practical reasons, the deodorizing stepwill normally be carried out at a temperature which is within the rangeof about 20° C. to about 70° C. Since the reaction is faster at highertemperatures, the amount of reaction time needed will decrease withincreasing temperature. For instance, at a temperature of about 20° C.,a residence time in the deodorizing step of one to three days may berequired. On the other hand, at a temperature of about 65° C., onlyabout two hours of reaction time is normally required.

The amount of time required for the aminoalcohol to react with theresidual n-butylacrylate monomer and residual acrylonitrile monomer willalso depend upon the level of aminoalcohol utilized. As a general rule,from about 0.05 weight percent to about 2 weight percent of theaminoalcohol will be added, based upon the total weight of the emulsion.More typically from about 0.1 weight percent to about 1.5 weight percentof the aminoalcohol will be added. It is normally preferred to utilizefrom about 0.3 weight percent to about 1 weight percent of theaminoalcohol.

The rubbery polymer is recovered from the emulsion (latex) after theoptional deodorizing step. This can be accomplished by utilizingstandard coagulation techniques. For instance, coagulation can beaccomplished by the addition of salts, acids or both to the latex.

After the rubbery polymer is recovered by coagulation, it can be washedto further reduce odors. This can be accomplished by simply pouring orspraying water on the rubbery polymer. The rubbery polymer can also bewashed in a water bath. Such a washing step will, of course, furtherreduce the level of any odor. After being washed, the rubbery polymer isgenerally dried.

It is sometimes advantageous to convert the dry rubbery polymer into apowder to facilitate its usage. In this case, it will be beneficial toadd a partitioning agent to the rubbery polymer. Some representativeexamples of partitioning agents that can be employed include calciumcarbonate, emulsion polyvinyl chloride and silica. Calcium carbonate isa highly desirable partitioning agent that can be utilized in suchapplications.

The rubbery polymers of this invention can be blended withpolyvinylchloride to make leather-like compositions. These leatherycompositions offer an excellent combination of properties forutilization in making skin compounds for panels used in automotiveapplications. These leathery compositions can be prepared by blendingthe rubbery polymer into polyvinylchloride (PVC) utilizing standardmixing techniques. It is highly preferred for the rubbery polymer to bein powdered form when blended into PVC to make such leatherycompositions.

A wide variety of plasticizers that are compatible with the polyvinylchloride resins can be employed. Some representative examples ofplasticizers which are highly suitable for this application includeabietic derivatives, such as hydroabietyl alcohol, methyl abietate andhydrogenated methyl abietate; acetic acid derivatives, such ascumylphenyl acetate; adipic acid derivatives, such as benzyloctyladipate, dibutyl adipate, diisobutyl adipate, di-(2-ethylhexyl) adipate,diisononyl adipate, diisooctyl adipate, dinonyl adipate, C₇₋₉ linearadipate, dicapryl adipate, octyl decyl adipate (n-octyl, n-decyladipate), straight chain alcohol adipate, didecyl adipate (diisodecyladipate), dibutoxyethyl adipate, high molecular weight adipate,polypropylene adipate, modified polypropylene adipate; azelaic acidderivatives, such as dicyclohexyl azelate, di-(2-ethylhexyl) azelate,di-n-hexyl azelate, low temperature plasticizer, diisooctyl azelate;benzoic acid derivatives such as diethylene glycol dibenzoate,dipropylene glycol dibenzoate, diethylene glycol benzoate anddipropylene glycol benzoate blend, proprietary low stain, neopentylglycol dibenzoate, glyceryl tribenzoate, timethylolethane tribenzoate,pentaerythritol tribenzoate, cumylphenyl benzoate; polyphenylderivatives such as hydrogenated terphenyl; citric acid derivatives,such as triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate,acetyl tri-n-butyl citrate, acetal tributyl citrate; epoxy derivativessuch as butyl epoxy stearate, epoxy-type plasticizer, epoxy-typeplasticizer tallate, alkyl epoxy stearate, epoxidized butyl ester,epoxidized octyl tallage, epoxidized soybean oil, epoxidizedtriglyceride, epoxidized soya bean oil, epoxidized sunflower oil,epoxidized-type plasticizer, epoxidized linseed oil, epoxidized tallateester, 2-ethylhexyl-epoxy tallate, octyl epoxy stearate; proprietaryesters such as proprietary ester and mixed ester; ether derivatives,such as cumylphenyl benzyl ether; formal derivatives such as2-(2-butoxyethoxy)ethanal; fumaric acid derivatives, such as dibutylfumarate, diisooctyl fumarate, dioctyl fumarate; glutaric acidderivatives such as mixed dialkyl glutarates and dicumylphenylglutarate; glycol derivatives such as diethylene glycol dipelargonate,triethylene glycol dipelargonate, triethylene glycol di-(2-ethylbutyrate), triethylene glycol di-caprylate-caprate, triethylene glycoldi-(2-ethylhexoate), triethylene glycol dicaprylate, tetraethyleneglycol dicaprylate, polyethylene glycol di-(2-ethylhexoate), butylphthalyl butyl glycolate, triglycolester of vegetable oil fatty acid,triethylene glycol ester of fatty acid; linear dibasic acid derivativessuch as mixed dibasic ester; petroleum derivatives such as aromatichydrocarbons; isobutyric acid derivatives such as2,2,4-trimethyl-1,3-pentanediol diisobutyrate; isophthalic acidderivatives such as di(2-ethylhexyl) isophthalate, diisooctylisophthalate, dioctyl isophthalate; lauric acid derivatives such asbutyllaurate, 1,2-propylene glycol monolaurate, ethylene glycolmonoethyl ether laurate, ethylene glycol monobutyl ether laurate,glycerol monolaurate, polyethylene glycol-400-dilaurate; mellitates suchas n-octyl, n-decyl trimellitate, tri-n-octyl-n-decyl trimellitate,triisononyl trimellitate, triisooctyl trimellitate, tricapryltrimellitate, diisooctyl monoisodecyl trimellitate, triisodecyltrimellitate, tri(C₇₋₉ alkyl) trimellitate, tri-2-ethylhexyltrimellitate; nitrile derivatives such as fatty acid nitrile; oleic acidderivatives such as butyl oleate, 1,2-propylene glycol mono oleate,ethylene glycol monobutyl ether oleate, tetrahydrofurfuryl oleate,glyceryl monoleate; paraffin derivatives such as chlorinated paraffins,diethylene glycol dipelargonate, triethylene glycol dipelargonate,2-butoxyethyl dipelargonate; phenoxy plasticizers such as acetylparacumyl phenol; phosphoric acid derivatives such as tri-(2-ethylhexyl)phosphate, tributoxyethyl phosphate, triphenyl phosphate, cresyldiphenyl phosphate, tricresyl phosphate, tri-isopropylphenyl phosphate,alkyl aryl phosphates, diphenyl-xylenyl phosphate, phenylisopropylphenyl phosphate; phthalic acid derivatives such as alkylbenzene phthalates, dimethyl phthalate, dibutyl phthalate, diisobutylphthalate, dihexyl phthalate, butyl octyl phthalate, butyl isodecylphthalate, butyl ISO-hexyl phthalate, diisononyl phthalate, dioctylphthalate, di-(2-ethyl hexyl) phthalate, n-octyl-n-decyl phthalate,hexyl octyl decyl phthalate, didecyl phthalate diisodecyl phthalate,diisodecyl phthalate, diundecyl phthalate, butyl-ethylhexyl phthalate,butylbenzyl phthalate, octylbenzyl phthalate, dicyclohexyl phthalate,diphenyl phthalate, alkylaryl phthalates and 2-ethylhexylisodecylphthalate; ricinoleic acid derivatives such as methylacetyl ricinoleate,n-butyl acetyl ricinoleate, glyceryl triacetyl ricinoleate; sebacic acidderivatives such as dimethyl sebacate, dibutyl sebacate, anddibutoxyethyl sebacate; stearic acid derivatives such as glyceryltri-acetone stearate, butyl acetoxy stearate, methylpentachlorostearate,and methoxylethyl acetoxy stearate; sucrose derivatives such as sucrosebenzoate; sulfonic acid derivatives such as alkyl-sulfonic esters ofphenol; tall oil derivatives such as methylester of tall oil andisooctyl ester of tall oil; and terephthalic acid derivatives such asdioctyl terephthalate.

Such leathery compositions typically contain from about 40 to 160 partsby weight of the rubbery polymer, from about 10 to about 50 parts of aplasticizer and from about 0.1 to about 5 parts by weight of anantidegradant per 100 parts by weight of the polyvinylchloride. It istypically preferred for such leathery compositions to contain from about60 to about 120 parts by weight of the rubbery polymer, from about 15 toabout 40 parts of the plasticizer and from about 0.5 to 3 parts of anantidegradant (per 100 parts of the PVC). It is typically more preferredfor the leathery composition to contain from about 70 to about 90 partsby weight of the rubbery polymer, from about 20 to about 30 parts byweight of the plasticizer and from about 1 to 2 parts by weight of theantidegradant per 100 parts by weight of the PVC.

Such compositions will also generally contain anacrylonitrile-butadiene-styrene resin (ABS resin). The leatherycomposition will typically contain from about 15 parts to about 80 partsof ABS resin per 100 parts of PVC. The leathery composition willpreferably contain from about 25 to about 55 parts per weight of the ABSresin per 100 parts by weight of the PVC. It is generally more preferredfor the leathery composition to contain from about 30 to about 40 partsby weight of the ABS resin per 100 parts by weight of PVC. Variouscolorants and/or pigments will typically also be added to thecomposition to attain a desired color.

The leathery compositions of this invention are useful in a wide varietyof applications. For example, they have been found to be extremelyvaluable when used in making skins for automotive panels. Such panelsare typically comprised of a semi-rigid urethane foam which is supportedby a rigid backing and covered with the leathery composition of thisinvention. Such skins are made by calendering the leathery compositionsof this invention and then cutting them to the desired size and shape.Such skins for automotive applications which are made with the leatherycompositions of this invention offer outstanding heat and ultravioletlight stability. These are highly desirable characteristics which canhelp to prevent the skin of automotive panels from cracking during thenormal life of the vehicle.

The rubbery polymers of this invention can also be blended with otherhalogen containing polymers (in addition to PVC), styrenic polymers(polymers which contain styrene, such as acrylonitrile-styrene-acrylate(ASA) polymers), polyolefins and polyamides to produce compositionswhich exhibit good heat and ultraviolet light resistance. Such polymericcompositions can be used in manufacturing a wide variety of usefularticles, such as profiles, moldings, sheeting, flooring, wallcoverings, hose, cables, footwear, automotive instrument panels andautomotive door panels. Virtually any type of polyamide (nylon) can beutilized in preparing such blends. These nylons are generally preparedby reacting diamines with dicarboxylic acids. The diamines anddicarboxylic acids which are utilized in preparing such nylons willgenerally contain from about 2 to about 12 carbon atoms. However, nylonsthat can be utilized in such blends can also be prepared by additionpolymerization. Some representative examples of nylons which can be usedinclude nylon-6,6, nylon-6, nylon-7, nylon-8, nylon-9, nylon-10,nylon-11, nylon-12 and nylon-6,12. These nylons will typically have anumber average molecular weight which is within the range of about 8,000toabout 40,000 and will more typically have a number average molecularweight which is within the range of about 10,000 to about 25,000. Somerepresentative examples of polyolefins that can be used include linearlow density polyethylene, high density polyethylene, polypropylene,polybutylene and modified polyolefins, such as ethylene vinyl acetate(EVA).

This invention is illustrated by the following examples that are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of this invention or the manner in which it can be practiced.Unless specifically indicated otherwise, all parts and percentages aregiven by weight.

EXAMPLE 1

In this experiment, a rubbery polymer was madeutilizing the techniquesof this invention. The polymerization was conducted in a reactor havinga capacity of 10 gallons (37.85 liter). The reactor was equipped withtwo axially flow turbine agitators with baffles which were operated at150 rpm (revolutions per minute).

A buffer solution was made by mixing 339 grams of a 25 percent aqueoussolution of dodecylbenzenesulfonate, 56.5 grams of tetrasodiumpyrophosphate and 33.9 grams of potassium persulfate into 16.96 kg ofwater. A first monomer solution was made by mixing 9.04 kg of butylacrylate, 904 grams of acrylonitrile, 452 grams of methyl methacrylate,226 grams of ethylene glycol dimethacrylate, 28.25 grams oftertiary-dodecyl mercaptan and 904 grams of 1,3-butadiene, and a secondmonomer solution was made by mixing 1.22 kg of styrene, 548 grams ofacrylonitrile, 11.3 grams of tertiary-dodecyl mercaptan, 113 grams of a55 percent solution of divinylbenzene and 226 grams of 1,3-butadiene.

The reactor was evacuated for 30 minutes and then the buffer solutionwas introduced into the reactor. The first monomer solution was thencharged into the reactor and the polymerization medium was maintained ata temperature of 120° F. (49° C.). When the solids content of the latexreached 40 percent, the second monomer solution was charged into thereactor and the temperature of the polymerization medium was increasedto 175° F. (80° C.). After the solids content reached 43-45 percent, thetemperature was maintained at 175° F. (80° C.) for an additional 4 hoursto insure that a high conversion had been attained.

A 2000-gram sample of the latex synthesized was subsequently epoxidizedby slowly adding 15 grams of formic acid and 10 grams of acetic acid in200 mls of water to the sample. Then, 70 grams of a 35 percent solutionof hydrogen peroxide was stirred into the latex. The latex containingthe formic acid, the acetic acid and the hydrogen peroxide was then putin a jug and placed in an oven at 110°-120° F. (43°-49° C.) for 3-4hours. Then, 37 grams of Aquamix 192 antioxidant was added and the latexwas coagulated. The rubbery polymer recovered was washed twice anddried. The rubbery polymer synthesized in this experiment containedabout 10 percent bound butadiene monomer.

EXAMPLE 2

In this experiment, a rubbery polymer containing 8 percent boundbutadiene was synthesized utilizing the technique of this invention. Theprocedure described in Example 1 was repeated in this experiment exceptthat the amount of 1,3-butadiene employed in making the first monomersolution was decreased to 678 grams with the amount of butyl acrylateemployed in making the first monomer solution being increased to 9.266kg. The latex synthesized was also epoxidized and recovered utilizingthe procedure described in Example 1.

EXAMPLE 3

In this experiment, a rubbery polymer containing 4 percent boundbutadiene was synthesized utilizing the technique of this invention. Theprocedure described in Example 1 was repeated in this experiment exceptthat the amount of 1,3-butadiene employed in making the first monomersolution was decreased to 339 grams with the amount of butyl acrylateemployed in making the first monomer solution being increased to 9.605kg. In this experiment, the amount of 1,3-butadiene employed in makingthe second monomer solution was also decreased to 339 grams with theamount of butyl acrylate employed in making the second monomer solutionbeing increased to 9.605 kg. The latex synthesized was also epoxidizedand recovered utilizing the procedure described in Example 1.

The rubbery polymer sample was clear. In fact, the rubbery polymer hadsufficient clarity to allow print having 6-point font to be read througha 0.125-inch (3.175 mm) thick sheet of said rubbery polymer. Morespecifically, the rubbery polymer had sufficient clarity to allow theword "clear" printed in black letters on a white background using6-point type to be read through a 0.125-inch (3.175 mm) thick sheet ofthe rubber with the unaided eye under typical indoor illumination.

EXAMPLE 4

The rubbery polymer synthesized in Example 2 was compounded into astandard crash pad formulation and evaluated for color stability. It wasalso compared to a standard crash pad formulation made with a rubberypolymer having the same composition that had not been epoxidized. Thelight aging studies were conducted in a Q-U-V accelerated weatheringtester that was equipped with a UVB-313 lamp. One aging cycle consistedof 6 hours of light and 4 hours of 100 percent humidity at 65° C. withcontinuous repeated cycles to a total of 500 hours. The crash padformulation made utilizing the rubbery polymer synthesized in Example 2showed a Delta E color change of only about 2.5. The crash padformulation made utilizing the comparative polymer showed a Delta Ecolor change of about 7. Thus, the crash pad formulation made utilizingthe rubbery polymer of this invention showed much better colorstability.

EXAMPLE 5

In this experiment, a rubbery polymer was synthesized utilizing thepolymerization procedure described in Example 3. However, the latex madewas ozonated rather than epoxidized. This was accomplished by simplyintroducing ozone into the latex sample. After the ozonalysis had beencompleted, the rubbery polymer samples were recovered and dried asdescribed in Example 1.

Heat aging was conducted by the ASTM 573-78 air oven heat aging methodwith ASTM die C specimens. Tensile properties were determined before andafteraging with a United Model FM30-DM1VA tensile tester at 20 inchesper minute (50.8 cm/minutes) crosshead speed, 2.5 inch (6.35 cm) jawseparation and 1 inch (2.54 cm) benchmark. For comparative purpose, asample of rubbery polymer made without incorporating a conjugateddiolefin monomer therein was also evaluated. Since this comparativerubber did not contain double bonds, it was not ozonated.

    ______________________________________                                        Elongation vs. Heat Aging Time                                                Heat Aging Time                                                                            Ozonated Rubber                                                                           Comparative Rubber                                   ______________________________________                                        Original     158%         89%                                                  70 hours    181%        121%                                                 144 hours    157%        116%                                                 288 hours    147%        127%                                                 384 hours    143%        124%                                                 480 hours    115%         70%                                                 528 hours    125%         98%                                                 ______________________________________                                    

As can be seen from the table above, the ozonated rubbery polymers hadmuch better elongation characteristics than did their non-ozonatedcounterparts. This experiment accordingly shows that the ozonalysistechnique of this invention can be used to improve the tensileproperties of the rubbery polymers described herein.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention.

What is claimed is:
 1. A panel for automotive applications which iscomprised of a semirigid urethane foam which is supported by a rigidbacking, wherein said semirigid urethane foam is covered with a leatheryskin which is comprised of (1) polyvinyl chloride, (2) a plasticizer and(3) a rubbery polymer which is comprised of repeat units which arecomprised of (a) butyl acrylate, or optionally a mixture of butylacrylate and 2-ethylhexyl acrylate containing up to about 40 percent2-ethylhexyl acrylate, (b) at least one member selected from the groupconsisting of methyl methacrylate, ethyl methacrylate, methyl acrylateand ethyl acrylate, (c) acrylonitrile, (d) styrene, (e) a conjugateddiolefin monomer and (f) a crosslinking agent, wherein said rubberypolymer is epoxidized.
 2. A panel as specified in claim 1 wherein saidleathery skin is comprised of about 40 to about 160 parts by weight ofthe rubbery polymer, from about 10 to about 50 parts by weight of theplasticizer and from about 0.1 to about 5 parts by weight antidegradantsper 100 parts by weight of the polyvinylchloride.
 3. A panel asspecified in claim 2 wherein said leathery skin is further comprised ofabout 15 to about 80 parts by weight of anacrylonitrile-butadiene-styrene resin per 100 parts of thepolyvinylchloride.
 4. A panel as specified in claim 3 wherein thecrosslinking agent is selected from the group consisting of difunctionalacrylates, trifunctional acrylates, difunctional methacrylates,trifunctional methacrylates and divinylbenzene.
 5. A panel as specifiedin claim 4 wherein said leathery skin contains from about 60 to about120 parts by weight of the rubbery polymer, from about 15 to about 40parts by weight of the plasticizer and from about 0.5 to 3 parts byweight antidegradants.
 6. A panel as specified in claim 5 wherein saidleathery skin contains from about 25 to about 55 parts by weight of theacrylonitrile-butadiene-styrene resin per 100 parts by weight ofpolyvinylchloride.
 7. A panel as specified in claim 6 wherein saidleathery skin is further comprised of a color imparting agent selectedfrom the group consisting of colorants and pigments.
 8. A panel asspecified in claim 7 wherein the conjugated diolefin monomer is1,3-butadiene.
 9. A panel as specified in claim 8 wherein the memberselected from the group consisting of methyl methacrylate, ethylmethacrylate, methyl acrylate and ethyl acrylate is methyl methacrylate.10. A panel as specified in claim 9 wherein said leathery skin containsfrom about 70 to about 90 parts by weight of the rubbery polymer, fromabout 20 to about 30 parts by weight of the plasticizer and from about 1to 2 parts by weight antidegradants per hundred parts by weight of thepolyvinylchloride.
 11. A panel as specified in claim 10 wherein thecrosslinking agent is divinylbenzene.
 12. A panel as specified in claim11 wherein said leathery skin contains from about 25 to about 55 partsby weight of the acrylonitrile-butadiene-styrene resin per 100 parts byweight of polyvinylchloride.
 13. A panel as specified in claim 10wherein the crosslinking agent is a trifunctional acrylate.
 14. A panelas specified in claim 10 wherein the crosslinking agent is adifunctional acrylate.
 15. A panel as specified in claim 10 wherein thecrosslinking agent is a difunctional methacrylate.
 16. A panel asspecified in claim 10 wherein the crosslinking agent is a